The objectives of this proposal are to detect and characterize embryonic and oncofetal antigens of various embryonic systems and a tumor system, and to assess the involvement of these antigens in preimplantation mouse embryogenesis and tumor growth. Immunological techniques for antigen recognition and functions will be employed and include: 1) mixed lymphocyte reactions, 2) cell-mediated lympholysis, 3) lymphocyte-induced growth inhibition, 4) antibody-induced growth inhibition, 5) cross-reactivity of serologically defined and lymphocyte defined antigens, 6) scanning electron microscope localization of defined antigens on preimplantation mouse embryos, and 7) in vivo evaluation of embryonic antigen sensitized lymphocytes in tumor rejection. These experiments should further our understanding of the role of oncofetal antigens in preimplantation mouse development and tumor growth.